mercredi 1 octobre 2008

Aquila 10

α, 1.3, pale yellow.

Altair is from a part of the Arabic name for the constellation; but occasionally is written Althair, Athair, Attair, and Atair; this last readers of Ben Hur will remember as the name of one of the shaykh Ilderim's horses in the chariot race at Antioch. And the word has been altered to Alcair, Alchayr, and Alcar.In the Syntaxis it was Ἀετός, one of Ptolemy's few stellar titles, probably first applied to α, and after the formation of the figure transferred to the latter, as in other instances in the early days of astronomy. Even six or seven centuries before Ptolemy it was referred to as Αἰετόςº where the chorus in the ῾Ρῆσος, until recently attributed to Euphrates, says:What is the star now passing?the answer being:The Pleiades show themselves in the east,The Eagle soars in the summit of heaven.It is supposed that long antecedent to this it was the Euphratean Idχu, the Eagle, or Erigu, the Powerful Bird, inscriptions to this effect being quoted by Brown, who thinks that it also was the Persian Muru, the Bird; the Sogdian Shad Mashir, and the Khorasmian Sadmasjij, the Noble Falcon.In Mr. J. F. Hewitt's Essays on the Ruling Races of Prehistoric Times it is asserted that later Zend mythology knew Altair as Vanant, the Western Quarter of the heavens, which earlier had been marked by our Corvus.With β and γ it constituted the twenty-first nakshatra Çravana, the Ear, and probably was at first so drawn, although also known as Çrona, Lame, or as Açvattha, the Sacred Fig Tree, Vishnu being regent of the asterism; these stars representing the Three Footsteps with which that god strode through the heavens, a Trident being the symbol.In China α, β, and γ were Ho Koo, a River Drum.In astrology Altair was a mischief-maker, and portended danger from reptiles.Ptolemy, who designated the degrees of star brilliancy by Greek letters, applied β to this as being of the 2d magnitude, whence some think that it has increased in light since his day. It is now the standard 1st magnitude according to the Pogson, or "absolute," photometric scale generally adopted by workers in stellar photometry, and is largely used in determining lunar distances at sea; while Flamsteed made it the fundamental reference star in his observations on the sun and in the construction of his catalogue.Its parallax, A parallax of 1ʺ represents a distance from the earth of 3.26 light years; a light year, the astronomers' unit in measuring stellar distances, — light traveling 186,327 miles in a second of time, — being about 63,000 times the distance of the earth from the sun. But no star thus far investigated has so large a parallax; that of the nearest, α Centauri, being only 0ʺ.75, 0ʺ.214, considered by Elkin as nearly or quite exact, indicates a distance of about 15 1/5 light years.Its spectrum is of Pickering's class Xb of Secchi's first type, but peculiar, with very hazy solar lines between the broad hydrogen lines.Altair has the large proper motion of 0ʺ.65 annually; and Gould thought it slightly variable.It marks the junction of the right wing with the body, and rises at sunset about the 15th of June, culminating on the 1st of September.Near it appeared, in A.D. 389, an object, whether a temporary star or a comet is not now known, said by Cuspinianus to have equaled Venus in brilliancy, which vanished after three weeks' visibility; and there is record of another, of sixty years previous, in the constellation.5° to the eastward of Altair, according to Denning, lies the radiant point of the Aquilids, the meteor stream visible from the 7th of June to the 12th of August.

β, 3.9, pale orange.

Alshain is from Shahin, a portion of the Persian name for the constellation; but Al Achsasi termed it Al Unuḳ al Ghurāb, the Raven's Neck.It is the southern of the two stars flanking Altair; yet, although it bears the second letter, is not as bright as γ or δ.

γ, 3, pale orange.

Tarazed, or Tarazad, from the same Persian title, lies north of Altair.These three stars constitute the Family of Aquila, the line joining them being 5° in length.Just north of γ is π, the only pretty and fairly easy double in the constellation. The components, of 6 and 6.8 magnitudes, 1ʺ.5 apart, are at a position angle of 120°.7.δ, η, and θ, of 3d to 4th magnitudes, in Antinoüs, were Al Mizān, the Scale-beam, of early Arabia, from their similar direction and nearly equal distances apart.

ε, 4.3, and ζ, 3.3, green.

each of these is known as Deneb, from Al Dhanab al ʽOḳāb, the eagle's Tail, which they mark.In China they were Woo and Yuë, names of old feudal states.η, in Antinoüs, is a noteworthy short-period variable of the 2d type, discovered by Pigott in 1784, yellow in tint, and fluctuating in brilliancy from 3.5 to 4.7 in a period of about seven days and four hours, and thus a convenient and interesting object of observation for midsummer evenings.Its spectrum is similar to that of our sun, and Lockyer and Belopolsky think it a spectroscopic binary.θ was the Chinese Tseen Foo, Heavenly Raft.

ι, 4.3, and λ, 3.6,

were Al Thalīmain, the Two Ostriches, by some confusion with the not far distant stars of like designation in Sagittarius; but the Grynaeus Syntaxis of 1538 gave λ, with some others unlettered, as belonging to the Dolphin.ι, with δ, η, and κ, was Yew Ke in China, the Right Flag; ρ being Tso Ke, the Left Flag.λ, with h, g, and some stars in Scutum, was Tseen Peen, the Heavenly Casque.